The present invention relates to a surround reproduction technique using a speaker array.
A speaker array apparatus of the delay array system uses a technique in which, a plurality of speakers which are arranged linearly or planarly, outputs identical audio signals while applying delay times slightly different from one another to the audio signals so as to simultaneously reach the focal point in the space, so that the acoustic energy in the vicinity of the focal point is enhanced by in-phase addition with the result that a sound beam having a strong directivity in the focal direction is produced. In the speaker array apparatus, the delay process is performed for each of audio signals of multi channels (for example, C: center channel, FL: front L channel, FR: front R channel, SL: rear L channel, and SR: rear R channel). The delay-processed signals of the all channels are added together and then supplied to the speakers, whereby the sound beams for the multi channels can be simultaneously output with different directionalities (for example, Patent Reference 1).
When the technique disclosed in Patent Reference 1 is used, as shown in FIG. 10, a related speaker array apparatus 1000 can control the sound beams for the channels so as to reflect off the wall faces of a room 100 and then reach the listening position. Therefore, the listener 200 at the listening position perceives that the sound image is localized in the directions toward the wall faces, and sounds are emitted from the speaker array apparatus 1000 in the front side and also from virtual speakers 300-FL, 300-FR, 300-SL, 300-SR, and hence an excellent surround effect can be obtained.
In Patent Reference 1, furthermore, a technique is disclosed in which, in the case where the localized sound image is laterally asymmetric with respect to the listener 200 depending on the shape of the room 100, a phantom that is a virtual sound image is formed by a plurality of beams, and the sound image is symmetrically localized. In the case where the direction of localizing the sound image of the front R channel is to be changed, for example, the sound for the front R channel is mixed with the sound beam for the center channel, so that the direction of localizing the sound image of the front R channel is changed toward the direction of the sound image of the center channel.
[Patent Reference 1] JP-A-2006-13711
In such a speaker array apparatus which uses the reflection from wall faces, when the room has a usual shape (for example, a rectangular shape), and sound beams are reflected twice at the maximum off the wall faces and then reach the listener 200, the limitation is that the sound image is localized in five directions. Although it is not impossible to increase the directions in which the sound image is localized if sound beams are reflected three times off the wall faces, the control of the sound beams is very difficult.